1. Field of Invention
This invention relates generally to disposable containers, specifically to an insulated cup made of sheet material.
2. Prior Art
There are three main types of disposable cups now in use: polystyrene, expanded resin, and paper.
Polystyrene cups are aesthetically pleasing, but they can be used only for holding cold drinks, and are not biodegradable or easily recyclable.
Cups of expanded synthetic resin material, sold under the trademark Styrofoam, are excellent thermal insulators, so that they can maintain the temperature of a drink, whether hot or cold, for long periods of time. They are comfortable to handle because their exteriors stay close to ambient temperature, regardless of the temperature of the drink. However they are environmentally unfriendly because they are not biodegradable or easily recyclable. As a result, they are being banned from many municipalities.
Standard single-layer paper cups are recyclable and biodegradable and therefore more environmentally sound. However they are poor thermal insulators, so that a beverage in a paper cup quickly warms (if cold) or cools (if hot). They are also uncomfortable to handle because a hot or cold drink can burn or uncomfortably cool a hand. Also a cold drink will cause condensation to appear on the outside, making a paper cup slippery and difficult to hold. Their single-layer construction makes them fragile, so that large cups filled with liquid easily crumble after prolonged handling.
Multi-layered paper cups have been designed for providing thermal insulation and increased strength. U.S. Pat. Nos. 2,661,889 to Phinney (1948), 4,993,580 to Smith (1991), 5,092,485 to Lee (1992), and 5,205,473 to Coffin (1993) show three-layered cups with smooth outer and inner shells, and a corrugated middle layer. The corrugated layer provides air pockets or spaces for thermal insulation and added strength to withstand prolonged handling.
Although strong and thermally efficient, these cups are all expensive and impractical to manufacture because their three layers are formed separately and then assembled together. This requires at least three adhesive joints for the forming the layers into "tapered cylinders" (conoids), two adhesive joints for assembling the layers together, and an adhesive joint for attaching the bottom. Some cups require even more adhesive joints. The liberal use of glue renders the cups difficult or impossible to recycle. The layers are usually formed from blanks cut separately from sheets, so that they do not make the most efficient use of paper and machinery time. Furthermore, the extra steps slow the production process, prevent the cups from being made on standard, existing cup-forming machinery. Also they increase manufacturing overhead and direct labor allocation, so that the prior-art cups are expensive. As a result, these cups have never achieved commercial success.
Although similar in its multilayered design, conventional corrugated boxboard also has never achieved commercial success for use in forming conoidal drinking cups because its layers are permanently fixedly adhered to one another. This makes it physically impracticable to bend or wrap boxboard into a smooth conoidal shape.
Often establishments selling very hot or cold beverages in paper cups will use double or nested cups to avoid the above problems of single paper cups, but doubling cups is time consuming and expensive.
The above Sadlier patent discloses a three-layered cup having smooth outer and inner layers and a corrugated middle layer, all formed of one continuous sheet wound in a spiral. Although more economical to manufacture than prior-art cups, this cup preferably is made by unidirectionally winding three layers on a spinning mandrel. It therefore cannot be readily manufactured by existing mass production cup-forming machinery, which typically wraps a cup's sidewall blank vertically into a conoidal shape, around a non-spinning mandrel.
The cup of the above Sadlier patent, and the cups of the above CIP applications, while a major improvement over existing cups, have an outer layer or shell which sometimes tends to slip down through the holder's fingers, especially when filled with liquid. Also such cups' insulating properties, while far superior to existing cups, especially considering the amount of material used, are not as great as possible. Further, such cups are not as comfortable to hold as is desirable since the area of contact between the holder's fingers and the cup is large, resulting in a relatively large amount of heat transfer, making the cup less comfortable to hold when it contains cold or hot liquid. In addition, prior-art-single-walled cups usually are printed on the outside to show graphics or the trademark of their manufacturer or a fast-food chain that dispenses them; such printing uses ink that consumes natural resources, makes recycling more difficult, and requires an extra step in production for printing. Such single-walled cups cannot be embossed instead of printed with such graphics or trademarks since their single-walled construction may leak when they are embossed. Another disadvantage of the cups of the Sadlier patent is that they are made of paper blanks which are cut from large sheets in a manner which leaves relatively large wasted areas or trimmings left on the blank. Finally these cups are not as rigid as possible and can be crushed or folded by squeezing them with less force than would be desirable.
Objects and Advantages
Accordingly, several objects and advantages of the invention are to provide a cup which (a) is thermally insulating for comfortable handling and for maintaining the temperature of its contents, (b) is sturdy enough to withstand prolonged handling, (c) can be made of biodegradable and recyclable materials, (d) is easy and inexpensive to manufacture, (e) can be made by existing machinery, (f) has less tendency to slip down through a holder's fingers, especially when filled with liquid, (g) has greater insulating properties, (h) can be cut from a large sheet in a manner which leaves less waste areas or trimmings on the sheet, (i) is more rigid and resistant to crushing or folding, (j) provides a reduced area of hand contact when held so as to reduce the amount of heat transmission, either when filled with cold or hot liquid, (k) can be embossed on the outside with graphics or a trademark, and (l) does not have to be printed so as to save ink, natural resources, production costs, production steps, and make recycling easier.
Other objects are to provide an insulated cup which is simpler in construction, more economical to fabricate, can be fabricated in a variety of ways, does not require unidirectional winding on a spinning mandrel, and can be fabricated in one continuous in-line production process (from folding the blank to wrapping it around a mandrel to form a cylindrical or conoidal shell).
Further objects and advantages will become apparent from a study of the following description and the accompanying drawings.
Summary
In accordance with one embodiment of the invention, a thermally insulated cup is formed from one continuous, homogeneous sheet of paper having two spaced-apart smooth end or outer portions connected by a corrugated or otherwise deformed and insulating middle portion. The smooth end portions are folded over opposite sides of the corrugated portion. The folded sheet is wrapped or bent around a mandrel to form conoidal inner and outer shells that sandwich the corrugated portion therebetween. The ends of each smooth portion are sealed together. A bottom closure is attached to the inner shell. The resulting three-layered cup is strong, offers good thermal insulation for comfortable handling and for-maintaining the temperature of its contents, and can be formed on existing machinery. Alternatively the continuous sheet may be formed of separate sections which are adhered together. Further, the corrugated or otherwise insulating portion can be an outer, rather than a middle, portion. Moreover the starting sheet can have two portions, so that after folding, it is wrapped into a two-layered insulated cup, with the corrugated layer on the outside. In the three-layered embodiment, the outer shell may have embossing for greater resistance to slippage through one's hands and better insulating properties. The sidewall blanks may have chamfered or trimmed comers to reduce the amount of waste on the sheet from which they are cut, and one, two, or all three layers of the cup's sidewall may be rolled over to form a top rim with added rigidity.